1. Project Summary/Abstract The recent Zika virus (ZIKV) outbreaks has surprised the world because of its rapid spread through the America and its association with birth defects such as microcephaly in the newborns and other neurologic dysfunctions in adults such as the Guillain-Barr syndrome (GBS). However, we are currently challenged with the fact that we know very little about the ZIKV functionality, nor do we know why has ZIKV suddenly become so pathogenic. Attempts to rapidly assess the ZIKV functionality is further challenged by a wide range of host cells that ZIKV infects. Here, we propose a unique and combined research approach to meet these challenges. Specifically, we plan to use fission yeast as a surrogate system for the rapid functional analysis of the ZIKV genome followed by immediate translations in human neural cells and a ZIKV infection model. Fission yeast is a simple and single cell eukaryote that has been used extensively as a model organism to study human cell biology and virology. It is a very well-tested model to study highly conserved cellular activities such as those described ZIKV cytopathic effects on cellular growth, cell cycle regulation, chromosomal biology, and cell death. Thus, study of these ZIKV effects in fission yeast is not only clinically relevant to the ZIKV diseases but we can also expedite the functional characterization of the ZIKV genome. We are uniquely qualified for the proposed study because we have extensive experiences in functional analyses of viral genomes using fission yeast and in the associated mammalian studies on viral infections. In fact, we were the first to characterize the HIV-1 genome and to develop model systems in fission yeast to study HIV-1 viral protein R (Vpr) and proteases (PRs). Our study is further strengthen by the participation of a multidisciplinary team whose expertise covering the entire spectrum of the proposed study. Therefore, we should have a high likelihood of success in the proposed study. We hypothesize that the ZIKV diseases such as microcephaly or GBS are caused by viral pathogenicity factors that are intrinsic to all ZIKVs. Alternatively, new ZIKV variants have emerged as the results of gene mutations that have led to the adaptation of high pathogenicity. To test this hypothesis, we will focus on two Specific Aims (SAs). The SA1 is to quickly phenotype the ZIKV genome for the identification of pathogenicity factor(s), which will be further compared against genetically distinctive ZIKV viral variants to answer the question of whether the observed ZIKV pathogenicity is an intrinsic viral property or the newly acquired viral function. The SA2 is to develop anti-ZIKV drug testing and screening systems against the viral pathogenicity factor and the ZIKV NS2B/NS3 protease, the latter has already been used as a therapeutic target for other flaviviruses. The successful completion of the proposed experiments will 1) provide a genome-wide description of the ZIKV phenotypes, 2) identify viral pathogenic factors that are linked to individual ZIKV proteins, and 3) develop fission yeast cell-based systems for anti-ZIKV drug testing and screenings.